confused

Sooo... We had sex 8 days before my AF was due, I'm always regular, and here we are now going on 4 days after I was supposed to get AF, and nothing but BFNs... Really bad heartburn... No appetite... Slight cramping 2 days ago similar to "those" cramps... Nothing... Any advice? What could this be? Also what is better for testing? Digital or a pink dye as in which is more sensitive? Is it possible I am preg but it just hasn't shown up on the digital tests yet? Do they need more hormones? What is happening hahaha help me